1. Field of the Invention
The present invention relates generally to the field of power transmission systems, particularly systems for driving screw conveyors and similar material handling devices. More particularly, the invention relates to a technique for isolating a gear reducer used in such a drive system from contaminants, particularly those originating in the transferred materials.
2. Description of the Related Art
Various drive systems have been posed and are presently in use for powering material handling machinery, such as belt conveyors, screw conveyors, and so forth. Certain of these material handling applications present unique difficulties which must be considered in the original design of the drive system and its components. Moreover, because many of these systems require relatively high torque and low speed drives, gear reducers are commonly employed in mechanical drives to reduce the speed provided by a prime mover such as an electric motor or internal combustion engine. The application constraints must, therefore, be considered in the design and installation of the gear reducers.
Gear reducers are commonly configured with a single or multiple stages. In a single-stage gear reducer, power is input from a prime mover via an input shaft or hub. The input shaft carries a pinion or gear which intermeshes with an output gear supported on an output shaft or hub. Based upon the sizes and configurations of the input and output gearing, a speed reduction ratio is established between the input and output. Multiple-stage gear reducers include intermediate rotating assemblies which intermesh with the input and output assemblies. The overall gear reduction ratio is, then, a product of the successive reduction ratios of the series of stages.
A particular challenge in the application of gear reducers to material handling applications involves exclusion of foreign contaminants from the gear reducer housing, and containment of lubricant within the housing. Specifically, material handling applications such as screw conveyer drives necessarily involve placement of the drive machinery in what can be a difficult environment in terms of free contaminants. Because screw conveyors, in particular, may transport liquid, solid, semi-liquid, semi-solid, fine or course materials and media, an effective contaminant exclusion and sealing system must be provided to contain potentially harmful contaminants in the screw conveyor trough and prevent them from entering into the gear reducer housing. Within the housing, the gearing and bearing sets supporting the rotating assemblies are typically bathed or wetted by a lubricant, such as mineral oil. In addition to preventing the ingress of contaminants, then, it is often desirable to provide some type of sealing system to maintain the lubricant within the gear reducer housing.
Various approaches have been proposed for sealing gear reducer housings in applications such as screw conveyor drives. However, at present, no commercially available screw conveyor contaminant control system provides completely satisfactory performance. Specifically, where materials may migrate from a screw conveyor trough, or a similar conveyance component of the system, the contaminants may sometimes infiltrate into the gear reducer housing, despite external seals.
There remains a need, therefore, for an improved system for excluding contaminants from a gear reducer housing, particularly in screw conveyor drive applications and keeping them contained in the screw conveyor trough.
The invention provides an improved technique for protecting gear reducer components in material handling applications designed to respond to such needs. The system includes a series of barriers defined between the source of contaminants and the gear reducer internal components. These barriers include seals, as well as close clearances, mechanical shields, and spaces and cavities which both trap contaminants and allow contaminants to drop or be otherwise eliminated from the path between the contaminant source and the gear reducer, The technique may be applied to new drive systems, but may also be retrofitted to existing drive systems, such as during regular servicing. Moreover, in screw conveyor applications, components of the sealing and contaminant exclusion system may be integrally assembled with the gear reducer, while other components are assembled in an adapter used to couple the gear reducer drive to the screw conveyor trough. The system thus provides an effective series of barriers to contaminants which may be at least partially preassembled for easy installation.
In a presently preferred embodiment, a series of barriers are defined by the system components. First barriers are defined immediately adjacent to a screw conveyor trough, including the trough plate, and rings and seals associated with the trough plate. The rings and seals may be conveniently packaged with an adapter which serves to couple the gear reducer drive to the screw conveyor trough plate. The adapter includes an integral drop out area which permits contaminants, both liquid and solid, to be eliminated from the system. Additional seals and barriers are provided on an opposite side of the drop out area. Certain of these seal assemblies may be integral with the adapter, while others are integral with the gear reducer. Where the latter seal assemblies are provided as an original component of the gear reducer, the overall system does not require any special configuration of the gear reducer, but may be applied and defined during assembly of the overall drive system.